4 so far work fine
I've tried mine with about 4 units now, all of work fine:
WX 100 (Sennheiser)
Jabra 250V
Sony PS3 Headset
Plantronics (I forget the model number -- hooks around the ear with the short boom)
Oh, and another Sony headset. Don't recall the model number, it basically looks like a light saber.
It only seems to remember one at a time -- once you pair it with a different one, it doesn't remember the prior one. Sometimes also, it doesn't give you a visual representation that it's paired -- but the BT unit will start receiving.
For all units, it's got a wierd little "tickle" at the end of each received transmission. Vox works very well for all; so well I've opted to turn it off in leu of PTT (that works on the BT set -- push once to transmit, push again to stop transmit).
Lemme know if you've got more questions.
By the way, this is my first post! Hi!